Methods of producing foam structures from recycled metallized polyolefin material

ABSTRACT

A physically crosslinked, closed cell continuous foam structure derived from recycled metallized polyolefin material; polypropylene, polyethylene, or combinations thereof, a crosslinking agent, and a chemical blowing agent is obtained. The foam structure is obtained by extruding a structure comprising a foam composition, irradiating the extruded structure with ionizing radiation, and continuously foaming the irradiated structure.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 14/144,986, filed on Dec. 31, 2013, the entire contents ofwhich is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to foam structures from recycled metallizedpolyolefin material. More particularly, to crosslinked, closed cellcontinuous foam structures derived from recycled metallized polyolefinmaterial.

BACKGROUND OF THE INVENTION

Over the past three decades, manufacturing businesses have beensuccessful in recycling many types of wastes: newspapers, cardboard,aluminum, steel, glass, various plastics, etc. In the case of plastics,there are certain types of plastic waste that do not readily recycleinto commercially viable new products. One such type of waste ismetallized polyolefin material.

Metallized polyolefins are common in the food packaging industry asbarrier films. For example, metalized polyolefin films are used aspotato chip bags, snack bar wrappers, etc. Other applications ofmetalized polyolefin films, particularly polypropylene films, includethe packaging of electronic and medical devices as well as dielectricsin electronic film capacitors.

Another application of metallized polyolefins, particularlypolypropylene, is in the plating industry. Decorative chrome plating(trivalent chromium) of injection molded polypropylene is commonly foundon household and domestic appliances as well as on components of otherdurable and non-durable goods. In addition, also common is decorativevacuum metalizing of polypropylene and polyethylene molded parts andthermoformed sheets, for example, confectionary trays.

Metal plating of polypropylene moldings is also not limited todecorative applications. Engineering requirements such as EMI and RFIshielding, electro-static dissipation, wear resistance, heat resistance,and thermal and chemical barriers at times necessitates the metalplating of polypropylene moldings.

Currently, there are various methods and systems for reclaiming andrecycling these metallized polyolefins. Some methods separate the metalfrom the polyolefin; however, these methods are limited to very thickmetal layers. Other methods and systems do not involve separating themetal from the polyolefin. Until now, there have been very few uses forthis unseparated metallized polyolefin material. Thus, manufacturers ofthese metallized polyolefin products regularly send their metal-coatedpolyolefin waste to landfills instead of recycling them.

Sending any manufacturing waste to a landfill is undesirable. The costassociated with sending waste to a landfill is steadily increasing andthere are always environmental concerns with dumping any waste in alandfill.

SUMMARY OF THE INVENTION

Described are foam structures manufactured from recycled metallizedpolyolefin material and methods of making and using these structures. Insome embodiments, these methods and foam structures address the abovelandfill issues facing manufacturers of metallized polyolefin products.The inventors have found solutions whereby the use of recycledmetallized polyolefins in foams: (1) provide a useful outlet for wastemetallized polyolefins; (2) reduce manufacturing costs by avoidinglandfill expenditures and creating a new market for waste metallizedpolyolefin material; and (3) lower the carbon footprint for producers ofmetallized polyolefins. Described are formulations that utilize recycledmetallized polyolefin material and incorporates it into physicallycrosslinked, continuous foam structures with a closed cell morphology.

Some embodiments include methods of forming structures by extruding 5-75wt. % recycled metallized polyolefin material; 25-95 wt. %polypropylene, polyethylene, or combinations thereof; a crosslinkingagent; and a chemical blowing agent in an extruder. The extruder may bea co-rotating, twin screw extruder at a specific energy of at least0.090 kW·hr/kg, preferably at least 0.105 kW·hr/kg, and more preferablyat least 0.120 kW·hr/kg.

The recycled metallized polyolefin material fed into the extruder may besmall enough to pass through a standard sieve of about 0.375 inches.Furthermore, the recycled metallized polyolefin material may have hadmetal layer(s) with an overall thickness of 0.003-100 μm, preferably0.006-75 μm, and more preferably 0.01-50 μm, prior to being recycled. Inaddition, the feed to the extruder may contain polypropylene having amelt flow index of 0.1-25 grams per 10 minutes at 230° C. and/orpolyethylene having a melt flow index of 0.1-25 grams per 10 minutes at190° C. The crosslinking agent may be divinylbenzene and the chemicalblowing agent may be azodicarbonamide in the extruder feed.

In some embodiments, the extruded structure may be irradiated withionizing radiation. The extruded structure may be irradiated withionizing radiation up to 4 separate times, preferably no more thantwice, and more preferably only once. The ionizing radiation may bealpha rays, beta rays, gamma rays, or electron beams. Furthermore, theionizing radiation may be an electron beam with an acceleration voltageof 200-1500 kV, preferably 400-1200 kV, and more preferably 600-1000 kV.The dosage of the electron beam may be 10-500 kGy, preferably 20-300kGy, and more preferably 20-200 kGy. The ionizing radiation cancrosslink the extruded structure to a crosslinking degree of 20-75%, andpreferably 30-60%.

In some embodiments, the irradiated structure may also be foamed in acontinuous process to form a foam structure. The foaming may includeheating the irradiated structure with molten salt, radiant heaters,vertical hot air oven, horizontal hot air oven, microwave energy, or acombination thereof. In addition, the irradiated structure may bepre-heated prior to foaming. Furthermore, the final structure can haveclosed cells with an average closed cell size of 0.05-1.0 mm, andpreferably 0.1-0.7 mm. The foam structure can have a density of 20-250kg/m³, and preferably 30-125 kg/m³. In addition, the foam structure canhave a thickness of 0.2-50 mm, preferably 0.4-40 mm, more preferably0.6-30 mm, and even more preferably 0.8-20 mm.

Some embodiments include a foam structure containing 5-75 wt. % recycledmetallized polyolefin material; and 25-95 wt. % polypropylene,polyethylene, or combinations thereof. The recycled metallizedpolyolefin material in the foam structure may have had metal layer(s)with an overall thickness of 0.003-100 μm, preferably 0.006-75 μm, andmore preferably 0.01-50 μm, prior to being recycled. In addition, thefoam structure may contain polypropylene having a melt flow index of0.1-25 grams per 10 minutes at 230° C. and/or polyethylene having a meltflow index of 0.1-25 grams per 10 minutes at 190° C.

In some embodiments, the foam structure can have closed cells with anaverage closed cell size of 0.05-1.0 mm, preferably 0.1-0.7 mm, and thedensity of the foam structure may be 20-250 kg/m³, preferably 30-125kg/m³. In addition, the foam structure may have a crosslinking degree of20-75%, and preferably 30-60%. Furthermore, the foam structure can havea thickness of 0.2-50 mm, preferably 0.4-40 mm, more preferably 0.6-30mm, and even more preferably 0.8-20 mm.

In addition, in some embodiments the foam structure may be slit,friction sawed, sheared, heat cut, laser cut, plasma cut, water jet cut,die-cut, mechanically cut, or manually cut to form an article.

Some embodiments include a laminate that includes a first layercontaining a foam structure containing 5-75 wt. % recycled metallizedpolyolefin material; and 25-95 wt. % polypropylene, polyethylene orcombinations thereof. The embodiment may also include a second layer.The second layer may be a film, fabric, fiber layer, a leather, orcombinations thereof. In addition, the second layer may also be a solidhardwood floor panel, an engineered wood floor panel, a laminate floorpanel, a vinyl floor tile, a ceramic floor tile, a porcelain floor tile,a stone floor tile, a quartz floor tile, a cement floor tile, a concretefloor tile, or combinations thereof.

The recycled metallized polyolefin material in the first layer may havehad metal layer(s) with an overall thickness of 0.003-100 μm, preferably0.006-75 μm, and more preferably 0.01-50 μm, prior to being recycled. Inaddition, the first layer may contain polypropylene having a melt flowindex of 0.1-25 grams per 10 minutes at 230° C. and/or polyethylenehaving a melt flow index of 0.1-25 grams per 10 minutes at 190° C.

Some embodiments include a thermoformed article that includes a foamstructure. The foam structure may contain 5-75 wt. % recycled metallizedpolyolefin material; and 25-95 wt. % polypropylene, polyethylene orcombinations thereof.

Furthermore, some embodiments include a flooring system containing a topfloor layer; a sub-floor layer; and at least one underlayment layerdisposed between the sub-floor and top floor layers. The underlaymentlayer may contain a foam structure. The foam structure may contain 5-75wt. % recycled metallized polyolefin material; and 25-95 wt. %polypropylene, polyethylene or combinations thereof.

The term “consist essentially of” means that the composition consistsalmost exclusively of the specified components except that additionalunspecified component substances which do not materially affect thebasic and novel characteristics of this invention can also be present.For example, the foam structure may include organic peroxides,antioxidants, lubricants, thermal stabilizers, colorants, flameretardants, antistatic agents, and other additives that do not impairinherent performance thereof.

Additional advantages of this invention will become readily apparent tothose skilled in the art from the following detailed description. Aswill be realized, this invention is capable of other and differentembodiments, and its details are capable of modifications in variousobvious respects, all without departing from this invention.Accordingly, the examples and description are to be regarded asillustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will now be described withreference to the accompanying figures, in which:

FIG. 1A is a cross sectional photo of the foam structure of Example 1 inthe machine direction;

FIG. 1B is a cross sectional photo of the foam structure of Example 1 inthe cross-machine direction;

FIG. 2A is a cross sectional photo of the foam structure of Example 2 inthe machine direction; and

FIG. 2B is a cross sectional photo of the foam structure of Example 2 inthe cross-machine direction.

DETAILED DESCRIPTION OF THE INVENTION

Described are methods of producing crosslinked, closed cell foamstructures derived from recycled metallized polyolefins. The methods forproducing a crosslinked, closed cell foam structure from recycledmetallized polyolefin material may include the steps of (a) extrusion,(b) irradiation, and (c) foaming. Also described are foam structuresmanufactured from recycled metallized polyolefin material.

In the extrusion step, a foam composition can be fed into an extruder.The method of feeding ingredients into the extruder is based on thedesign of the extruder and the material handling equipment available.Preblending ingredients of the foam composition may be performed, ifnecessary, to facilitate their dispersal. A Henshel mixer is preferablyused for such preblending. All ingredients can be preblended and fedthru a single port in the extruder. The ingredients can also beindividually fed thru separate designated ports for each ingredient. Forexample, if the crosslinking agent or any other additive is a liquid,the agent and/or additives can be added through a feeding gate (orgates) on the extruder or through a vent opening on the extruder (ifequipped with a vent) instead of being preblended with solidingredients. Combinations of “preblending” and individual ingredientport feeding can also be employed.

The foam composition fed into the extruder can contain about 5 to about75 wt. % recycled metallized polyolefin material, preferably from about10 to about 70 wt. %, and more preferably from about 20 to about 60 wt.%. Recycled metallized polyolefin material is available in variousforms. Examples include, but are not limited to: pellets, granules,chips, flakes, beads, cylinders, rods, fluff, and powder. In someembodiments, recycled metallized polyolefin material can be obtained ashomogenous pellets utilizing the process disclosed in WO 2013057737 A2,which is hereby incorporated by reference in its entirety. In someembodiments, chips or flakes of recycled metallized polyolefin materialcan be obtained from plastic chippers and shredders commonly used toreduce the size of waste profiles, injection molded pieces, etc. In athird example, pulverized metallized polyolefin material can be obtainedfrom commercial pulverizing equipment or cryogenic pulverization.

Regardless of the form, it is preferred that the recycled materialpieces be reduced in size to pass thru a standard sieve of about 0.375inches (9.5 mm). Recycled pieces that do not pass thru a standard sieveof about 0.375 inches (9.5 mm) are difficult to sufficiently shear andmix with other ingredients within the extruder. Thus, a homogenousstructure may not be obtained. A structure includes, but is not limitedto, layers, films, webs, sheets, or other similar structures.

The primary sources of metallized polyolefins are the metalizing andmetal coating industries. These industries employ various techniques toobtain metallized polyolefins, including vacuum metallization, arc orflame spraying, electroless plating, or electroless plating followed byelectroplating. The coatings are often not limited to one metalliclayer. Polyolefin coated with multiple layers of varying metalsdeposited using different techniques can also be used in the disclosedinvention.

Metallized polyolefins can be obtained by vacuum metallization, arc orflame spraying, electroless plating, or electroless plating followed byelectroplating. Each technique to obtain metallized polyolefins isbriefly described as follows:

In vacuum metallization, a metal is evaporated in a vacuum chamber. Thevapor then condenses onto the surface of the substrate, leaving a thinlayer of metal coating. This deposition process is also commonly calledphysical vapor deposition (PVD).

In flame spraying, a hand-held device is used to spray a layer ofmetallic coating on the substrate. The primary force behind depositionis a combustion flame, driven by oxygen and gas. Metallic powder isheated and melted. The combustion flame accelerates the mixture andreleases it as a spray.

Arc spraying is similar to flame spraying, but the power source isdifferent. Instead of depending on a combustion flame, arc sprayingderives its energy from an electric arc. Two wires, composed of themetallic coating material and carrying DC electric current, touchtogether at their tips. The energy that releases, when the two wirestouch, heats and melts the wire, while a stream of gas deposits themolten metal onto the surface of the substrate, creating a metal layer.

In electroless plating, the surface of the plastic is etched away usingan oxidizing solution. The surface becomes extremely susceptible tohydrogen bonding as a result of the oxidizing solution and typicallyincreases during the coating application. Coating occurs when thepolyolefin component (post-etching) is immersed in a solution containingmetal ions, which then bond to the plastic surface as a metal layer.

In order for electroplating (electrolytic plating) to be successful, thepolyolefin surface must first be rendered conductive, which can beachieved through electroless plating. Once the polyolefin surface isconductive, the substrate is immersed in a solution. In the solution aremetallic salts, connected to a positive source of current (cathode). Ananodic (negatively charged) conductor is also placed in the bath, whichcreates an electrical circuit in conjunction with the positively chargedsalts. The metallic salts are electrically attracted to the substrate,where they create a metal layer. As this process happens, the anodicconductor, typically made of the same type of metal as the metallicsalts, dissolves into the solution and replaces the source of metallicsalts, which is depleted during deposition.

The amount of coating that can be deposited by each technique varies.Depending on the end use requirements, one technique may be preferableover another. Nonetheless, the metal coatings deposited by thesetechniques will range from about 0.003 μm for a single layer to 100 μmfor a multi-layer coating, preferably from 0.006 μm for a single layerto 75 μm for a multi-layer coating, and more preferably from 0.01 to μmfor a single layer to 50 μm for a multi-layer coating. The metal in therecycled metallized polyolefins varies from about 0.05 to about 5 wt. %.

The most common metal coating applied to polyolefins is aluminum. Lesscommon coatings are trivalent chromium, nickel, and copper. Even lesscommon coatings are, but not limited to, tin, hexavalent chromium, gold,silver, as well as co-deposited metals such as nickel-chromium. Thoseskilled in the art will appreciate that these metal coatings are notnecessarily pure elemental coatings. For example, “nickel” may benickel-phosphorus or nickel-boron alloy and “copper” may be copper-zincalloy (brass) or copper-tin alloy (bronze). Regardless of whether themetal is or isn't alloyed, the specific metal is still the primarycomponent of the coating. It is preferred that the metallic coatingcontain 70-100% of the named metal, more preferably 80-100% of the namedmetal, and even more preferably 85-100% of the named metal. Thoseskilled in the art will also appreciate that the surface of the metallayers can be oxidized, and some of the metals, tarnished.

Both polypropylene and polyethylene films can be vacuum metalized in thefilm metallizing industry. It should thus be expected that any recycledmetallized polyolefin can contain at least one polypropylene, or atleast one polyethylene, or a mixture of both. For barrier applications(rather than decorative applications), both polypropylene andpolyethylene films may be coextruded with other barrier layer materials,such as EVOH and PVOH. In such instances, these multilayer films requireadhesive “tie layers” to bond the EVOH and PVOH to the polypropylene orpolyethylene. These tie layers range in polyolefins from OBC topolyethylene with acetate or ester groups to polyethylene ionomers.

Likewise, polypropylenes and polyethylenes grafted with maleic anhydrideare also used in the industry to improve adhesion, not only withadjoining EVOH or PVOH but also with the metal coatings.

In the metal coatings industry, polypropylene may often be preferredover polyethylene. However, due to the broader end use requirements forarticles produced in this industry, polypropylenes may be blended withother olefins to meet, for example, softness requirements, impactrequirements, or adhesion requirements, etc. Thus, it should be expectedthat any recycled metallized polyolefin from this industry may be ablended polyolefin.

The polypropylene(s) comprising the polyolefin component of the recycledmetallized polyolefin may contain an elastic or softening component,typically an ethylene, α-olefin, or rubber component. Thus, the term“polypropylene” in this disclosure includes, but is not limited to,polypropylene, impact modified polypropylene, polypropylene-ethylenecopolymer, metallocene polypropylene, metallocene polypropylene-ethylenecopolymer, metallocene polypropylene olefin block copolymer (with acontrolled block sequence), polypropylene based polyolefin plastomer,polypropylene based polyolefin elasto-plastomer, polypropylene basedpolyolefin elastomer, polypropylene based thermoplastic polyolefin blendand polypropylene based thermoplastic elastomeric blend.

A non-limiting example of “polypropylene” is an isotactichomopolypropylene. Commercially available examples include, but are notlimited to, FF018F from Braskem and 3271 from Total Petrochemicals.

A non-limiting example of an “impact modified polypropylene” is ahomopolypropylene with ethylene-propylene (EP) copolymer rubber. Therubber can be amorphous or semicrystalline but is not in sufficientquantities to render the material any plastomeric or elastomericproperties. A few non-limiting examples of commercially available“impact modified polypropylene” are TI4015F and TI4015F2 from Braskemand Pro-fax® 8623 and Pro-fax® SB786 from LyondellBasell.

“Polypropylene-ethylene copolymer” is polypropylene with random ethyleneunits. A few non-limiting examples of commercially available“polypropylene-ethylene copolymer” are 6232, 7250FL, and Z9421 fromTotal Petrochemicals, PP4772 from ExxonMobil, and TR3020F from Braskem.

“Metallocene polypropylene” is metallocene syndiotactichomopolypropylene, metallocene atactic homopolypropylene, andmetallocene isotactic homopolypropylene. Non-limiting examples of“metallocene polypropylene” are those commercially available under thetrade names METOCENE™ from LyondellBasell and ACHIEVE™ from ExxonMobil.Metallocene polypropylenes are also commercially available from TotalPetrochemicals and include, but are not limited to, grades M3551,M3282MZ, M7672, 1251, 1471, 1571, and 1751.

“Metallocene polypropylene-ethylene copolymer” is metallocenesyndiotactic, metallocene atactic, and metallocene isotacticpolypropylene with random ethylene units. Commercially availableexamples include, but are not limited to, Lumicene® MR10MX0 andLumicene® MR60MC2 from Total Petrochemicals and Purell® SM170G fromLyondellBasell.

“Metallocene polypropylene olefin block copolymer” is a polypropylenewith alternating crystallizable hard “blocks” and amorphous soft“blocks” that are not randomly distributed—that is, with a controlledblock sequence. An example of “metallocene polypropylene olefin blockcopolymer” includes, but is not limited to, the INTUNE™ product linefrom the Dow Chemical Company.

“Polypropylene based polyolefin plastomer” (POP) and “polypropylenebased polyolefin elastoplastomer” are both metallocene andnon-metallocene propylene based copolymers with plastomeric andelastoplastomeric properties. Non-limiting examples are thosecommercially available under the trade name VERSIFY™ (metallocene) fromthe Dow Chemical Company, VISTAMAXX™ (metallocene) from ExxonMobil, andKOATTRO™ (non-metallocene) from LyondellBasell (a butene-1 based line ofplastomeric polymers—certain are butene-1 homopolymer based and othersare polypropylene-butene-1 copolymer based materials).

“Polypropylene based polyolefin elastomer” (POE) is both metallocene andnon-metallocene propylene based copolymer with elastomeric properties.Non-limiting examples of propylene based polyolefin elastomers are thosepolymers commercially available under the trade names THERMORUN™ andZELAS™ (non-metallocene) from Mitsubishi Chemical Corporation, ADFLEX™and SOFTELL™ (both non-metallocene) from LyondellBasell, VERSIFY™(metallocene) from the Dow Chemical Company, and VISTAMAXX™(metallocene) from ExxonMobil.

“Polypropylene based thermoplastic polyolefin blend” (TPO) ispolypropylene, polypropylene-ethylene copolymer, metallocenehomopolypropylene, and metallocene polypropylene-ethylene copolymer,which have ethylene-propylene copolymer rubber in amounts great enoughto give the thermoplastic polyolefin blend (TPO) plastomeric,elastoplastomeric or elastomeric properties. Non-limiting examples ofpolypropylene based polyolefin blend polymers are those polymer blendscommercially available under the trade names EXCELINK™ from JSRCorporation, THERMORUN™ and ZELAS™ from Mitsubishi Chemical Corporation,FERROFLEX™ and RxLOY™ from Ferro Corporation, and TELCAR™ from TeknorApex Company.

“Polypropylene based thermoplastic elastomer blend” (TPE) ispolypropylene, polypropylene-ethylene copolymer, metallocenehomopolypropylene, and metallocene polypropylene-ethylene copolymer,which have diblock or multiblock thermoplastic rubber modifiers (SEBS,SEPS, SEEPS, SEP, SERC, CEBC, HSB and the like) in amounts great enoughto give the thermoplastic elastomer blend (TPE) plastomeric,elastoplastomeric, or elastomeric properties. Non-limiting examples ofpolypropylene based thermoplastic elastomer blend polymers are thosepolymer blends commercially available under the trade name DYNAFLEX® andVERSAFLEX® from GLS Corporation, MONPRENE® and TEKRON® from Teknor ApexCompany and DURAGRIP® from Advanced Polymers Alloys (a division of FerroCorporation).

All of the above polypropylenes may be grafted with maleic anhydride.Non-limiting examples are ADMER® QF500A and ADMER® QF551A for MitsuiChemicals. It should be noted that most commercial anhydride-graftedpolypropylenes also contain rubber.

The term “polyethylene” includes, but is not limited to, LDPE, LLDPE,VLDPE, VLLDPE, HDPE, polyethylene-propylene copolymer, metallocenepolyethylene, metallocene ethylene-propylene copolymer, and metallocenepolyethylene olefin block copolymer (with a controlled block sequence).

“Metallocene polyethylene” is metallocene based polyethylene withproperties ranging from non-elastic to elastomeric. Non-limitingexamples of metallocene polyethylene are commercially available underthe trade name ENGAGE™ from Dow Chemical Company, ENABLE™ and EXCEED™from ExxonMobil, and EXACT™ from Borealis.

“VLDPE” and “VLLDPE” are very low density polyethylene and very lineardensity low density polyethylene containing an elastic or softeningcomponent, typically α-olefins. Non-limiting examples of VLDPE andVLLDPE are commercially available under the tradename FLEXOMER™ from theDow Chemical Company and particular grades of STAMYLEX™ from Borealis.

“Metallocene polyethylene olefin block copolymer” is a polyethylene withalternating crystallizable hard “blocks” and amorphous soft “blocks”that are not randomly distributed—that is, with a controlled blocksequence. An example of “metallocene polyethylene olefin blockcopolymer” includes, but is not limited to, the INFUSE™ product linefrom the Dow Chemical Company.

All of the above polyethylenes may be grafted with maleic anhydride.Non-limiting commercially available examples are ADMER® NF539A fromMitsui Chemicals, BYNEL® 4104 from DuPont, and OREVAC® 18360 fromArkema. It should be noted that most commercial anhydride-graftedpolyethylenes also contain rubber.

These polyethylenes may also be copolymers and terpolymers containingacetate and/or ester groups. The comonomer groups include, but are notlimited to, vinyl acetate, methyl acrylate, ethyl acrylate, butylacrylate, glycidyl methacrylate, and acrylic acid. Non-limiting examplesare commercially available under the tradename BYNEL®, ELVAX® andELVALOY® from DuPont; EVATANE®, LOTADER®, and LOTRYL® from Arkema;ESCORENE™, ESCOR™, and OPTEMA™ from ExxonMobil.

These polyethylenes may also be copolymer and terpolymer ionomerscontaining acetate and/or ester groups. A common comonomer group is, butis not limited to, methacrylic acid. Non-limiting examples arecommercially available under the tradename SURLYN® from DuPont; IOTEK™from ExxonMobil, and AMPLIFY™ IO from Dow Chemical Company.

The polymer component of the recycled metallized polyolefin may alsocontain EVOH and/or PVOH (“PVA”). “EVOH” is a copolymer of ethylene andvinyl alcohol. Non-limiting examples are commercially available underthe tradename EVAL™ and EXCEVAL™ from Kuraray and SOARNOL™ from NipponGohsei. “PVOH” is a polyvinyl alcohol. Non-limiting examples arecommercially available under the tradename ELVANOL® from DuPont andPOVAL®, MOWIOL®, and MOWIFLEX® from Kuraray.

The foam composition fed into the extruder also can contain about 25 toabout 95 wt. %, preferably about 30 to about 90 wt. %, and morepreferably about 40 to about 80 wt. %, of at least one polypropylenehaving a melt flow index from about 0.1 to about 25 grams per 10 minutesat 230° C. and/or at least one polyethylene having a melt flow indexfrom about 0.1 to about 25 grams per 10 minutes at 190° C. In someembodiments, the melt flow index of the polypropylene(s) and/orpolyethylene(s) is preferably from about 0.3 to about 20 grams per 10minutes at 230° C. and at 190° C., respectively, and more preferablyfrom about 0.5 to about 15 grams per 10 minutes at 230° C. and at 190°C., respectively.

The “melt flow index” (MFI) value for a polymer is defined and measuredaccording to ASTM D1238 at 230° C. for polypropylenes and polypropylenebased materials and at 190° C. for polyethylenes and polyethylene basedmaterials using a 2.16 kg plunger for 10 minutes. The test time may bereduced for relatively high melt flow resins.

The MFI provides a measure of flow characteristics of a polymer and isan indication of the molecular weight and processability of a polymermaterial. If the MFI values are too high, which corresponds to a lowviscosity, extrusion according to the present disclosure cannot besatisfactorily carried out. Problems associated with MFI values that aretoo high include low pressures during extrusion, problems setting thethickness profile, uneven cooling profile due to low melt viscosity,poor melt strength and/or machine problems. Problems with MFI valuesthat are too low include high pressures during melt processing, sheetquality and profile problems, and higher extrusion temperatures whichcause a risk of foaming agent decomposition and activiation.

The above MFI ranges are also important for foaming processes becausethey reflect the viscosity of the material and the viscosity has aneffect on the foaming. Without being bound by any theory, it is believedthere are several reasons why particular MFI values are far moreeffective. A lower MFI material may improve some physical properties asthe molecular chain length is greater, creating more energy needed forchains to flow when a stress is applied. Also, the longer the molecularchain (MW), the more crystal entities the chain can crystallize thusproviding more strength through intermolecular ties. However, at too lowan MFI, the viscosity becomes too high. On the other hand, polymers withhigher MFI values have shorter chains. Therefore, in a given volume of amaterial with higher MFI values, there are more chain ends on amicroscopic level relative to polymers having a lower MFI, which canrotate and create free volume due to the space needed for such rotation(e. g., rotation occurring above the T_(g), or glass transitiontemperature of the polymer). This increases the free volume and enablesan easy flow under stress forces.

These polypropylene(s) and/or polyethylene(s) with specific MFI valuesinclude the same types described earlier That is, the polypropyleneincludes, but is not limited to, polypropylene, impact modifiedpolypropylene, polypropylene-ethylene copolymer, metallocenepolypropylene, metallocene polypropylene-ethylene copolymer, metallocenepolypropylene olefin block copolymer (with a controlled block sequence),polypropylene based polyolefin plastomer, polypropylene based polyolefinelasto-plastomer, polypropylene based polyolefin elastomer,polypropylene based thermoplastic polyolefin blend and polypropylenebased thermoplastic elastomeric blend. Furthermore, the polypropylenesmay be grafted with maleic anhydride. In addition, the polyethyleneincludes, but is not limited to, LDPE, LLDPE, VLDPE, VLLDPE, HDPE,polyethylene-propylene copolymer, metallocene polyethylene, metalloceneethylene-propylene copolymer, and metallocene polyethylene olefin blockcopolymer (with a controlled block sequence), any of which may containgrafted compatibilizers or copolymers that contain acetate and/or estergroups. As discussed previously, these polyethylenes may be grafted withmaleic anhydride. These polyethylenes may also be copolymers andterpolymers containing acetate and/or ester groups and may be copolymerand terpolymer ionomers containing acetate and/or ester groups.

Since a broad range of articles and laminates can be created with thedisclosed foam composition, a broad range of polypropylenes andpolyethylenes can be employed in the foam composition to meet thevarious end use requirements of the structures, articles, and laminates.

When relatively large or thick pieces of metal (in relation to the foamcell size) are present in the foam structure, undesirable “voids” and“large cells” may occur. Thus, including polypropylene and/orpolyethylene with grafted compatibilizers or copolymers that containacetate and/or ester groups as ingredients may be required to preventthe formation of these undesirable “voids” and “large cells”.

In addition, the foam composition fed into the extruder may also containfurther additives compatible with producing the disclosed foamstructure. Common additives include, but are not limited to, organicperoxides, antioxidants, lubricants, thermal stabilizers, colorants,flame retardants, antistatic agents, nucleating agents, plasticizers,antimicrobials, antifungals, light stabilizers, UV absorbents,anti-blocking agents, fillers, deodorizers, thickeners, cell sizestabilizers, metal deactivators, and combinations thereof.

Regardless of how all the ingredients are fed into the extruder, theshearing force and mixing within the extruder must be sufficient toproduce a homogenous structure. A co-rotating twin screw extruder canprovide sufficient shearing force and mixing thru the extruder barrel toextrude a structure with uniform properties.

Specific energy is an indicator of how much work is being applied duringthe extrusion of the ingredients and how intensive the extrusion processis. Specific energy is defined as the energy applied to a material beingprocessed by the extruder, normalized to a per kilogram basis. Thespecific energy is quantified in units of kilowatts of applied energyper total material fed in kilograms per hour. Specific energy iscalculated according to the formula:

${{{Specific}\mspace{14mu} {Energy}} = \frac{{KW}({applied})}{{feedrate}( \frac{kg}{hr} )}},{where}$${{KW}({applied})} = \frac{\begin{matrix}{{{KW}( {{motor}\mspace{14mu} {rating}} )}*( {\% \mspace{14mu} {torque}\mspace{14mu} {from}\mspace{14mu} {maximum}\mspace{14mu} {allowable}} )*} \\{{RPM}( {{actual}\mspace{14mu} {running}\mspace{14mu} {RPM}} )}\end{matrix}}{{Max}\mspace{11mu} {RPM}\; ( {{capability}\mspace{14mu} {of}\mspace{14mu} {extruder}} )*0.97( {{gearbox}\mspace{14mu} {efficiency}} )}$

Specific energy is used to quantify the amount of shearing and mixing ofthe ingredients within the extruder. The extruders used for the presentinvention are capable of producing a specific energy of at least 0.090kW·hr/kg, preferably at least 0.105 kW·hr/kg, and more preferably atleast 0.120 kW·hr/kg.

The extrusion temperature of the structure is preferably at least 10° C.below the thermal decomposition initiation temperature of the chemicalblowing agent. If the extrusion temperature exceeds the thermaldecomposition temperature of the blowing agent, then the blowing agentwill decompose, resulting in undesirable “prefoaming.”

The foam composition can include a variety of different chemical blowingagents. Examples of chemical blowing agents include, but are not limitedto, azo compounds, hydrazine compounds, carbazides, tetrazoles, nitrosocompounds, and carbonates. In addition, a chemical blowing agent may beemployed alone or in any combination.

One chemical blowing agent that can be used in some embodiments isazodicarbonamide (ADCA). ADCA's thermal decomposition typically occursat temperatures between about 190 to 230° C. In order to prevent ADCAfrom thermally decomposing in the extruder, extruding temperature ismaintained at or below 190° C.

If the difference between the decomposition temperature of the thermallydecomposable blowing agent and the melting point of the polymer with thehighest melting point is high, then a catalyst for blowing agentdecomposition may be used. Exemplary catalysts include, but are notlimited to, zinc oxide, magnesium oxide, calcium stearate, glycerin, andurea.

The lower temperature limit for extrusion is that of the polymer withthe highest melting point. If the extrusion temperature drops below themelting temperature of the polymer with the highest melting point, thenundesirable “unmelts” appear in the structure. Upon foaming, an extrudedstructure that was extruded below this lower temperature limit willexhibit uneven thickness, a non-uniform cell structure, pockets of cellcollapse, and other undesirable attributes.

The thickness of the extruded structure is about 0.1 to about 30 mm,preferably from about 0.2 to about 25 mm, more preferably from about 0.3to about 20 mm, and even more preferably from about 0.4 to about 15 mm.

After the structure has been produced by the extruder, the extrudedstructure can be subjected to irradiation with ionizing radiation at agiven exposure to crosslink the composition of the extruded structure,thereby obtaining an irradiated, crosslinked structure. Ionizingradiation is often unable to produce a sufficient degree of crosslinkingon polypropylene(s), polypropylene based materials, somepolyethylene(s), and some polyethylene based materials. Thus, acrosslinking agent is typically added to the foam composition that isfed into the extruder to promote crosslinking.

Examples of ionizing radiation include, but are not limited to, alpharays, beta rays, gamma rays, and electron beams. Among them, an electronbeam having uniform energy is preferably used to prepare the crosslinkedstructures. Exposure time, frequency of irradiation, and accelerationvoltage upon irradiation with an electron beam can vary widely dependingon the intended crosslinking degree and the thickness of the extrudedstructure. However, the ionizing radiation should generally be in therange of from about 10 to about 500 kGy, preferably from about 20 toabout 300 kGy, and more preferably from about 20 to about 200 kGy. Ifthe exposure is too low, then cell stability is not maintained uponfoaming. If the exposure is too high, the moldability of the resultingfoam structure may be poor. (Moldability is a desirable property whenthe foam structure is used in thermoforming applications.) Also, thestructure may be softened by exothermic heat release upon exposure tothe electron beam radiation such that the structure can deform when theexposure is too high. In addition, the polymer components may also bedegraded from excessive polymer chain scission.

The extruded structure may be irradiated up to 4 separate times,preferably no more than twice, and more preferably only once. If theirradiation frequency is more than about 4 times, the polymer componentsmay suffer degradation so that upon foaming, for example, uniform cellswill not be created in the resulting foam.

When the thickness of the extruded structure is greater than about 4 mm,irradiating each primary surface of the profile with an ionizedradiation is preferred to make the degree of crosslinking of the primarysurface(s) and the inner layer more uniform.

Irradiation with an electron beam provides an advantage in that extrudedstructures having various thicknesses can be effectively crosslinked bycontrolling the acceleration voltage of the electrons. The accelerationvoltage is generally in the range of from about 200 to about 1500 kV,preferably from about 400 to about 1200 kV, and more preferably about600 to about 1000 kV. If the acceleration voltage is less than about 200kV, then the radiation cannot reach the inner portion of the extrudedstructure. As a result, the cells in the inner portion can be coarse anduneven on foaming. Additionally, acceleration voltage that is too lowfor a given thickness profile will cause arcing, resulting in “pinholes”or “tunnels” in the foamed structure. On the other hand, if theacceleration voltage is greater than about 1500 kV, then the polymersmay degrade.

Regardless of the type of ionizing radiation selected, crosslinking isperformed so that the composition of the extruded structure iscrosslinked about 20 to about 75%, preferably about 30 to about 60%, asmeasured by the “Toray Gel Fraction Method.”

According to the “Toray Gel Fraction Method,” tetralin solvent is usedto dissolve non-crosslinked components in a composition. In principle,the non-crosslinked material is dissolved in tetralin and thecrosslinking degree is expressed as the weight percentage of crosslinkedmaterial in the entire composition.

The apparatus used to determine the percent of polymer crosslinkingincludes: 100 mesh (0.0045 inch wire diameter); Type 304 stainless steelbags; numbered wires and clips; a Miyamoto thermostatic oil bathapparatus; an analytical balance; a fume hood; a gas burner; a hightemperature oven; an anti-static gun; and three 3.5 liter wide mouthstainless steel containers with lids. Reagents and materials usedinclude tetralin high molecular weight solvent, acetone, and siliconeoil. Specifically, an empty wire mesh bag is weighed and the weightrecorded. For each sample, about 100 milligrams±about 5 milligrams ofsample is weighed out and transferred to the wire mesh bag. The weightof the wire mesh bag and the sample, typically in the form of foamcuttings, is recorded. Each bag is attached to the corresponding numberwire and clips. When the solvent temperature reaches 130° C., the bundle(bag and sample) is immersed in the solvent. The samples are shaken upand down about 5 or 6 times to loosen any air bubbles and fully wet thesamples. The samples are attached to an agitator and agitated for three(3) hours so that the solvent can dissolve the foam. The samples arethen cooled in a fume hood. The samples are washed by shaking up anddown about 7 or 8 times in a container of primary acetone. The samplesare washed a second time in a second acetone wash. The washed samplesare washed once more in a third container of fresh acetone as above. Thesamples are then hung in a fume hood to evaporate the acetone for about1 to about 5 minutes. The samples are then dried in a drying oven forabout 1 hour at 120° C. The samples are cooled for a minimum of about 15minutes. The wire mesh bag is weighed on an analytical balance and theweight is recorded.

Crosslinking is then calculated using the formula 100*(C−A)/(B−A), whereA=empty wire mesh bag weight; B=wire bag weight+foam sample beforeimmersion in tetralin; and C=wire bag weight+dissolved sample afterimmersion in tetralin.

Suitable crosslinking agents include, but are not limited to,commercially available difunctional, trifunctional, tetrafunctional,pentafunctional, and higher functionality monomers. Such crosslinkingmonomers are available in liquid, solid, pellet, and powder forms.Examples include, but are not limited to, acrylates or methacrylatessuch as 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate,ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, tetramethylol methane triacrylate,1,9-nonanediol dimethacrylate and 1,10-decanediol dimethacrylate; allylesters of carboxylic acid (such as trimellitic acid triallyl ester,pyromellitic acid triallyl ester, and oxalic acid diallyl ester); allylesters of cyanulic acid or isocyanulic acid such as triallyl cyanurateand triallyl isocyanurate; maleimide compounds such as N-phenylmaleimide and N,N′-m-phenylene bismaleimide; compounds having at leasttwo tribonds such as phthalic acid dipropagyl and maleic aciddipropagyl; and divinylbenzene. Additionally, such crosslinking agentsmay be used alone or in any combination. Divinylbenzene (DVB), adifunctional liquid crosslinking monomer, can be used as a crosslinkingagent in the present invention and added to the extruder at a level nogreater than 4% PPHR.

Crosslinks may be generated using a variety of different techniques andcan be formed both intermolecularly, between different polymermolecules, and intramolecularly, between portions of a single polymermolecule. Such techniques include, but are not limited to, providingcrosslinking agents which are separate from a polymer chain andproviding polymer chains which incorporate a crosslinking agentcontaining a functional group which can form a crosslink or be activatedto form a crosslink.

After irradiating the extruded structure, foaming may be accomplished byheating the crosslinked structure to a temperature higher than thedecomposition temperature of the thermally decomposable blowing agent.For the thermally decomposable blowing agent azodicarbonamide, thefoaming is performed at about 200 to about 260° C., preferably about 220to about 240° C., in a continuous process. A continuous foaming processis preferred over a batch process for production of a continuous foamsheet.

The foaming is typically conducted by heating the crosslinked structurewith molten salt, radiant heaters, vertical hot air oven, horizontal hotair oven, microwave energy, or a combination of these methods. Thefoaming may also be conducted in an impregnation process using, forexample, nitrogen in an autoclave, followed by a free foaming via moltensalt, radiant heaters, vertical hot air oven, horizontal hot air oven,microwave energy, or a combination of these methods. A preferredcombination of molten salt and radiant heaters is used to heat thecrosslinked structure.

Optionally, before foaming, the crosslinked structure can be softenedwith preheating. This helps stabilize the expansion of the structureupon foaming.

The density of the foam structure is defined and measured using sectionor “overall” density, rather than a “core” density, as measured by JISK6767. The foam structure produced using the above described method willyield foams with a section, or “overall” density of about 20 to about250 kg/m³, preferably about 30 kg/m³ to about 125 kg/m³. The sectiondensity can be controlled by the amount of blowing agent and thethickness of the extruded structure. If the density of the structure isless than about 20 kg/m³, then the structure does not foam efficientlydue to a large amount of chemical blowing agent needed to attain thedensity. Additionally, if the density of the structure is less thanabout 20 kg/m³, then the expansion of the structure during the foamingstep becomes increasingly difficult to control. Furthermore, if thedensity of the foam structure is less than 20 kg/m³, then the foamstructure becomes increasingly prone to cell collapse. Thus, it isdifficult to produce a foam structure of uniform section density andthickness from recycled metallized polyolefin material at a density lessthan about 20 kg/m³.

The foam structure is not limited to a section density of about 250kg/m³. A foam of about 350 kg/m³, about 450 kg/m³, or about 550 kg/m³may also be produced. However, it is preferred that the foam structurehave a density of less than about 250 kg/m³ since greater densities aregenerally cost prohibitive when compared to other materials which can beused in a given application.

The foam structure produced using the above method may have closedcells. Preferably, at least 90% of the cells have undamaged cell walls,preferably at least 95%, and more preferably more than 98%. The averagecell size is from about 0.05 to about 1.0 mm, and preferably from about0.1 to about 0.7 mm. If the average cell size is lower than about 0.05mm, then the density of the foam structure is typically greater than 250kg/m³. If the average cell size is larger than 1 mm, the foam will havean uneven surface. There is also a possibility of the foam structurebeing undesirably torn if the population of cells in the foam does nothave the preferred average cell size. This can occur when the foamstructure is stretched or portions of it are subjected to a secondaryprocess. The cell size in the foam structure may have a bimodaldistribution representing a population of cells in the core of the foamstructure which are relatively round and a population of cells in theskin near the surfaces of the foam structure which are relatively flat,thin, and/or oblong.

The thickness of the foam structure is about 0.2 mm to about 50 mm,preferably from about 0.4 mm to about 40 mm, more preferably from about0.6 mm to about 30 mm, and even more preferably from about 0.8 mm toabout 20 mm. If the thickness is less than about 0.2 mm, then foaming isnot efficient due to significant gas loss from the primary surfaces. Ifthe thickness is greater than about 50 mm, expansion during the foamingstep becomes increasingly difficult to control. Thus, it is increasinglymore difficult to produce a foam structure comprising recycledmetallized polyolefin material with uniform section density andthickness.

The desired thickness can also be obtained by a secondary process suchas slicing, skiving, or bonding. Slicing, skiving, or bonding canproduce a thickness range of about 0.1 mm to about 100 mm.

The disclosed foam structures can be used in a variety of applications.One application is foam tapes and gasketing. Closed cell foam tape iscommonly used in areas such as window glazing, where strips of foam tapeare placed between two window panes to seal the air between the glass.This improves the thermal insulation property of the window. The foamalso acts as a cushion for the glass panes from the effects of thermalexpansion and contraction of the building and window frame from dailyand seasonal temperature changes. Likewise, closed cell foam gaskets arecommonly used for sealing and cushioning. Handheld electronic devicesand household appliances are two examples that may contain foam gaskets.A soft, flexible foam structure is usually suited as a tape or gasket.

When the foam structure is to be used as a tape or gasket, a pressuresensitive adhesive layer may be disposed on at least a portion of one orboth major surfaces. Any pressure sensitive adhesive known in the artmay be used. Examples of such pressure sensitive adhesives include, butare not limited to, acrylic polymers, polyurethanes, thermoplasticelastomers, block copolymers, polyolefins, silicones, rubber basedadhesives, copolymers of ethylhexylacrylate and acrylic acid, copolymersof isooctyl acrylate and acrylic acid, blends of acrylic adhesives andrubber based adhesives as well as combinations of the foregoing.

The foam structure can also be thermoformed. To thermoform a layer ofthe foam structure, the foam must be heated to the melting point of thepolyolefin blend. If the blend has immiscible polymers, the blend mayexhibit more than one melting point. In this case, the foam structurecan typically be thermoformed when the foam is heated to a temperaturemidway between the foam composition's lowest melting point and highestmelting point.

One example of a thermoformed article is an automobile air duct. Aclosed cell foam structure is particularly suited for this applicationdue to its lower weight (when compared to solid plastic), its insulatingproperties that help maintain the temperature of the air flowing thruthe duct, and its resistance to vibration (versus solid plastic). A firmfoam structure is suited for an automobile air duct.

In some embodiments, the foam structures are laminates containing afirst layer of the foam composition and a second layer. In theselaminates, the foam composition or structure containing layer can, forexample, be combined with a film and/or foil. Examples of suitablematerials for such layers include, but are not limited to, polyvinylchloride (PVC); thermoplastic polyolefin (TPO); thermoplastic urethane(TPU); fabrics such as polyester, polypropylene, cloth and otherfabrics; leather and/or fiber layers such as non-wovens. Such layers maybe manufactured using standard techniques that are well known to thoseof ordinary skill in the art. Importantly, the foam of the disclosuremay be laminated on one or both sides with these materials and mayinclude multiple layers.

In these laminates, a layer may be joined to an adjacent layer by meansof chemical bonds, mechanical means and/or combinations of these.Adjacent laminate layers may also be affixed to each other by any othermeans including the use of attractive forces between materials havingopposite electromagnetic charges or attractive forces present betweenmaterials which both have either a predominantly hydrophobic characteror a predominantly hydrophilic character.

In some embodiments, the foam structures or laminates are used inautomobile interior parts such as door panels, door rolls, door inserts,door stuffers, trunk stuffers, armrests, center consoles, seat cushions,seat backs, headrests, seat back panels, instrument panels, kneebolsters, or a headliner. These foam structures or laminates can also beused in furniture (e.g., commercial, office, and residential furniture)such as chair cushions, chair backs, sofa cushions, sofa trims, reclinercushions, recliner trims, couch cushions, couch trim, sleeper cushions,or sleeper trims. These foam laminates or structures can also be used inwalls such as modular walls, moveable walls, wall panels, modularpanels, office system panels, room dividers, or portable partitions. Thefoam laminates or structures can also be used in storage casing (e.g.,commercial, office and residential) which is either mobile orstationary. Furthermore, the foam laminates and structures can also beused in coverings such as chair cushion coverings, chair back coverings,armrest coverings, sofa coverings, sofa cushion coverings, reclinercushion coverings, recliner coverings, couch cushion coverings, couchcoverings, sleeper cushion coverings, sleeper coverings, wall coverings,and architectural coverings.

Some embodiments include a first layer of the disclosed foam structureand a second layer selected from the group consisting of a solidhardwood floor panel, an engineered wood floor panel, a laminate floorpanel, a vinyl floor tile, a ceramic floor tile, a porcelain floor tile,a stone floor tile, a quartz floor tile, a cement floor tile, and aconcrete floor tile.

In these laminates, the first layer may be joined to the adjacent panelor tile by means of chemical bonds, mechanical means and/or combinationsof these. The adjacent laminate layers may also be affixed to each otherby any other means including the use of attractive forces betweenmaterials having opposite electromagnetic charges or attractive forcespresent between materials which both have either a predominantlyhydrophobic character or a predominantly hydrophilic character.

A popular method of attaching the disclosed foam to a floorpanel—particularly a solid hardwood floor panel, an engineered woodfloor panel, and a laminate floor panel—is via a pressure sensitiveadhesive layer that is disposed on at least a portion of the foamsurface and/or panel surface. Any pressure sensitive adhesive known inthe art may be used. Examples of such pressure sensitive adhesives areacrylic polymers, polyurethanes, thermoplastic elastomers, blockcopolymers, polyolefins, silicones, rubber based adhesives, copolymersof ethylhexylacrylate and acrylic acid, copolymers of isooctyl acrylateand acrylic acid, blends of acrylic adhesives and rubber based adhesivesas well as combinations of the foregoing.

The foam layer attached to the floor panel—particularly a solid hardwoodfloor panel, an engineered wood floor panel, and a laminate floorpanel—serves several purposes. The foam can reduce the reflected soundpressure level when the panel is impacted, for example, when walking onthe panel with boots or high heeled shoes. The foam can also act as amoisture vapor barrier between the panel and sub-floor and can helpprovide a more uniform laydown among multiple panels since anyunevenness, bumps, or spikes (for example a protruding nailhead) on thesub-floor will be buffered by the foam. These floor panels and tiles arecommonly installed in residential homes, office buildings, and othercommercial buildings.

Another embodiment of the present invention provides a flooring systemincluding: a top floor layer; a sub-floor layer; and one or moreunderlayment layers where at least one of the underlayment layerscontains the disclosed foam structure disposed between the sub-floor andthe top floor layer.

In this system, the foam layer may or may not be joined to any adjacentlayer, including the sub-floor or the top floor layer. When any layer inthe disclosed system is joined, the attachment is performed by means ofchemical bonds, mechanical means and/or combinations of these. Theadjacent layers may also be affixed to each other by any other meansincluding the use of attractive forces between materials having oppositeelectromagnetic charges or attractive forces present between materialswhich both have either a predominantly hydrophobic character or apredominantly hydrophilic character.

If any layers are attached, a popular method of attachment is the use ofeither a one component urethane adhesive, a two component urethaneadhesive, a one component acrylic adhesive, or a two component acrylicadhesive. The adhesive is typically applied during the installation ofthe system in residential homes, office buildings, and commercialbuildings.

The foam layer in this system serves several purposes. The foam canreduce the reflected sound pressure level when the top floor layer isimpacted, for example, when walking on the panel with boots or highheeled shoes. The foam can also act as a moisture vapor barrier betweenthe panel and sub-floor and help provide a more uniform laydown amongmultiple panels since any unevenness, bumps, or spikes (for example aprotruding nailhead) on the sub-floor will be buffered by the foam. Forcases where the top floor layer is composed of ceramic floor tiles,porcelain floor tiles, stone floor tiles, quartz floor tiles, cementfloor tiles, and concrete floor tiles connected by grout and where alllayers in the flooring system are joined, the foam can help reduce groutfracturing by buffering varying thermal expansions and contractions ofthe various layers in the system.

To satisfy the requirements of any of the above applications, thedisclosed structures of the present disclosure may be subjected tovarious secondary processes, including and not limited to, embossing,corona or plasma treatment, surface roughening, surface smoothing,perforation or microperforation, splicing, slicing, skiving, layering,bonding, and hole punching.

EXAMPLES Example 1

A commercial pulverized LLDPE having an MFI of 6.8 g/10 min (190° C.,2.16 kg), a commercial reactor flake polypropylene-ethylene copolymerhaving an MFI of 1.5 g/10 min (230° C., 2.16 kg), a masterbatchcontaining zinc oxide, a masterbatch containing a standard polyolefinanti-oxidant package, and divinylbenzene were mixed together and fedinto a co-rotating twin screw extruder. Simultaneously, tubes ofcompounded recycled aluminum metalized polypropylene film,azodicarbonamide, and standard polyolefin extrusion processing aid werefed thru other ports on the extruder. The tubes of recycled metalizedpolypropylene were cylinders of about 3 mm×2.5 mm OD×0.8 mm wallthickness and extrusion compounded from shredded film coated with about0.02-0.05 μm of aluminum. The three resins were fed into a co-rotatingtwin screw extruder at 60% LLDPE, 20% polypropylene-ethylene copolymer,and 20% recycled aluminum metalized polypropylene film.

After extrusion at a specific energy of 0.105 kW·hr/kg and at atemperature of 170° C., the sheet was crosslinked by electron beamradiation at a dosage of 57 kGy and then foamed continuously around 241°C. The content of azodicarbonamide and the thickness of the extrudedsheet was such that a foam structure of 40 kg/m³ density, 2.0 mmthickness, and 38% crosslinking was obtained. FIG. 1A is a cross sectionphoto of the foam structure of Example 1 in the machine direction andFIG. 1B is a cross section photo of the foam structure of Example 1 inthe cross-machine direction.

Example 2

A commercial pulverized LLDPE having an MFI of 6.8 g/10 min (190° C.,2.16 kg), a commercial reactor flake polypropylene-ethylene copolymerhaving an MFI of 1.5 g/10 min (230° C., 2.16 kg), a masterbatchcontaining zinc oxide, a masterbatch containing a standard polyolefinanti-oxidant package, and divinylbenzene were mixed together and fedinto a co-rotating twin screw extruder. Simultaneously, tubes ofcompounded recycled aluminum metalized polypropylene film,azodicarbonamide, and standard polyolefin extrusion processing aid werefed thru other ports on the extruder. The tubes of recycled metalizedpolypropylene were cylinders of about 3 mm×2.5 mm OD×0.9 mm wallthickness and extrusion compounded from shredded film coated with about0.02-0.05 μm of aluminum. The three resins were fed into a co-rotatingtwin screw extruder at 55% LLDPE, 5% polypropylene-ethylene copolymer,and 40% recycled aluminum metalized polypropylene film.

After extrusion at a specific energy of 0.105 kW·hr/kg and at atemperature of 170° C. the sheet was crosslinked by electron beamradiation at a dosage of 57 kGy and then foamed continuously around 241°C. The content of azodicarbonamide and the thickness of the extrudedsheet was such that a foam structure of 36 kg/m³ density, 2.0 mmthickness, and 34% crosslinking was obtained. FIG. 2A is a cross sectionphoto of the foam structure of Example 2 in the machine direction andFIG. 2B is a cross section photo of the foam structure of Example 2 inthe cross-machine direction.

Test Methods

The various properties in the above examples were measured by thefollowing methods:

The specific energy of the extruder is calculated according to theformula:

${{{Specific}\mspace{14mu} {Energy}} = \frac{{KW}({applied})}{{feedrate}( \frac{kg}{hr} )}},{where}$${{KW}({applied})} = \frac{\begin{matrix}{{{KW}( {{motor}\mspace{14mu} {rating}} )}*( {\% \mspace{14mu} {torque}\mspace{14mu} {from}\mspace{14mu} {maximum}\mspace{14mu} {allowable}} )*} \\{{RPM}( {{actual}\mspace{14mu} {running}\mspace{14mu} {RPM}} )}\end{matrix}}{{Max}\mspace{11mu} {RPM}\; ( {{capability}\mspace{14mu} {of}\mspace{14mu} {extruder}} )*0.97( {{gearbox}\mspace{14mu} {efficiency}} )}$

In general, preferred values of specific energy would be at least 0.090kW·hr/kg, preferably at least 0.105 kW·hr/kg, and more preferably atleast 0.120 kW·hr/kg.

The “density” of foam structure is defined and measured using section or“overall” density, rather than a “core” density, according to JIS K6767.In general, preferred values of density would be 20-250 kg/m³, and morepreferably 30-125 kg/m³.

“Crosslinking” is measured according to the “Toray Gel Fraction Method,”where tetralin solvent is used to dissolve non-crosslinked components.In principle, non-crosslinked material is dissolved in tetralin and thecrosslinking degree is expressed as the weight percentage of crosslinkedmaterial. The apparatus used to determine the percent of polymercrosslinking includes: 100 mesh (0.0045 inch wire diameter); Type 304stainless steel bags; numbered wires and clips; a Miyamoto thermostaticoil bath apparatus; an analytical balance; a fume hood; a gas burner; ahigh temperature oven; an anti-static gun; and three 3.5 liter widemouth stainless steel containers with lids. Reagents and materials usedinclude tetralin high molecular weight solvent, acetone, and siliconeoil. Specifically, an empty wire mesh bag is weighed and the weightrecorded. For each sample, about 2 grams to about 10 grams±about 5milligrams of sample is weighed out and transferred to the wire meshbag. The weight of the wire mesh bag and the sample, typically in theform of foam cuttings, is recorded. Each bag is attached to thecorresponding number wire and clips. When the solvent temperaturereaches 130° C., the bundle (bag and sample) is immersed in the solvent.The samples are shaken up and down about 5 or 6 times to loosen any airbubbles and fully wet the samples. The samples are attached to anagitator and agitated for three (3) hours so that the solvent candissolve the foam. The samples are then cooled in a fume hood. Thesamples are washed by shaking up and down about 7 or 8 times in acontainer of primary acetone. The samples are washed a second time in asecond acetone wash. The washed samples are washed once more in a thirdcontainer of fresh acetone as above. The samples are then hung in a fumehood to evaporate the acetone for about 1 to about 5 minutes. Thesamples are then dried in a drying oven for about 1 hour at 120° C. Thesamples are cooled for a minimum of about 15 minutes. The wire mesh bagis weighed on an analytical balance and the weight is recorded.Crosslinking is then calculated using the formula 100*(C−A)/(B−A), whereA=empty wire mesh bag weight; B=wire bag weight+foam sample beforeimmersion in tetralin; and C=wire bag weight+dissolved sample afterimmersion in tetralin. In general, preferred values of crosslinkingdegree are 20-75%, and more preferably 30-60%.

The “melt flow index” (MFI) value for a polymer is defined and measuredaccording to ASTM D1238 at 230° C. for polypropylenes and polypropylenebased materials and at 190° C. for polyethylenes and polyethylene basedmaterials using a 2.16 kg plunger for 10 minutes. The test time may bereduced for relatively high melt flow resins.

This application discloses several numerical ranges in the text andfigures. The numerical ranges disclosed inherently support any range orvalue within the disclosed numerical ranges even though a precise rangelimitation is not stated verbatim in the specification because thisinvention can be practiced throughout the disclosed numerical ranges.

The above description is presented to enable a person skilled in the artto make and use the invention, and is provided in the context of aparticular application and its requirements. Various modifications tothe preferred embodiments will be readily apparent to those skilled inthe art, and the generic principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the invention. Thus, this invention is not intended to belimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein. Finally,the entire disclosure of the patents and publications referred in thisapplication are hereby incorporated herein by reference.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. A foam structure comprising: 5-75 wt. %recycled metallized polyolefin material; 25-95 wt. % polypropylene,polyethylene, or combinations thereof.
 2. The foam structure of claim 1comprising polypropylene having a melt flow index of 0.1-25 grams per 10minutes at 230° C.
 3. The foam structure of claim 1 comprisingpolyethylene having a melt flow index of 0.1-25 grams per 10 minutes at190° C.
 4. The foam structure of claim 1, wherein the density of thefoam structure is 20-250 kg/m³.
 5. The foam structure of claim 1,wherein the foam structure has a crosslinking degree of 20-75%.
 6. Thefoam structure of claim 1, wherein the foam structure has an averageclosed cell size of 0.05-1.0 mm.
 7. The foam structure of claim 1,wherein the foam structure has a thickness of 0.2-50 mm.
 8. The foamstructure of claim 1, wherein the foam structure is slit, frictionsawed, sheared, heat cut, laser cut, plasma cut, water jet cut, die-cut,mechanically cut, or manually cut to form an article.
 9. A laminatecomprising: a first layer comprising a foam structure, wherein the foamstructure comprises 5-75 wt. % recycled metallized polyolefin material;25-95 wt. % polypropylene, polyethylene or combinations thereof; and asecond layer.
 10. The laminate of claim 9, wherein the second layer isselected from the group consisting of a film, a fabric, a fiber layer,and a leather.
 11. The laminate of claim 9, wherein the second layer isselected from the group consisting of a solid hardwood floor panel, anengineered wood floor panel, a laminate floor panel, a vinyl floor tile,a ceramic floor tile, a porcelain floor tile, a stone floor tile, aquartz floor tile, a cement floor tile, and a concrete floor tile.
 12. Athermoformed article comprising a foam structure, wherein the foamstructure comprises 5-75 wt. % recycled metallized polyolefin material;and 25-95 wt. % polypropylene, polyethylene, or combinations thereof.13. A flooring system comprising: a top floor layer; a sub-floor layer;and at least one underlayment layer disposed between the sub-floor andtop floor layers, wherein at least one underlayment layer comprises afoam structure, wherein the foam structure comprises 5-75 wt. % recycledmetallized polyolefin material; and 25-95 wt. % polypropylene,polyethylene, or combinations thereof.